Percussive tool



May l, 1962 R. R. VINCENT 3,032,013

. PERcussIvE TooL Filed Dec. 7, 1960 INVENTOR. ROBERT I//NcE/vr .4T T ORNE Y nited States This invention pertains generally to expansible cham- Iber motors of the reciprocating hammer type and pertains especially to improved means for varying the stroke of the hammer.

Motors of this generaltype are commonly employed in hand heldpercussive tools actuated by compressed air or an equivalent motive fluid. In accordance with conventional practice, the expansible chamber of such tools is dened by a longitudinal bore in the cylinder, a stationary abutment closing one end of the bore and a sliding abutment consisting of a reciprocable piston. A iiuid distributing valve automatically controls the reciprocation of the piston; and, the distribution valve typically provides the aforementioned stationary abutment for the expansible chamber.

In certain percuSsive tool-s of the aforedescribed character, such as chipping hammers and the like, it is desirable that the intensity of the hammer blows delivered to a work impacting implement be adjustable in order to meet changing requirements of a given application and l to accommodate widely diversilied applications. Therefore, the broad object of the present invention is to provide an expansible chamber motor for a percussive tool wherein the intensity of the blows of the reciprocating hammer piston may be selectively adjusted over a wide range without varying the amount of pressure uid admitted to the motor.

Another object is to provide an expansible chamber motor of the aforesaid type wherein the hammer piston stroke may be selectively adjusted by lengthening or shortening the motor chamber.

atent Still another object is to provide annular spacer elements for axially lengthening the cylinder bore of an expansible chamber motor, said elements being adapted for stacking one upon the other to displace axially the motor cylinder from a uid distributing valve comprising the stationary abutment for the motor. p o

A more specic object is to provide a number of like spacer elements of the aforedescribed typeone or more of which may be stacked between the fluid distributing valve and the cylinder to provide a number of like spacing increments equalto the number of spacer elements.

Another specific object is to provide a detachable cylinder head for the cylinder which provides a housing for the uid distributing valve and the spacer elements wherein the spacer elements may be conveniently and compactly stored when not performing their intended spacing function.

Yet another object is to provide a blow-varying means for a percussive air motor which is characterized by ease of operation, simplicity of construction and low manufacturing cost.

These and other objects and advantages will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings in which:

FIGURE 1 is a longitudinal sectional View of an expansible chamber motor constructed in accordance with the present invention;

FIG. 2 is a fragmentary View similar to FIG. 1 illustrating an alternative arrangement of certain parts shown in FIG. l;

FIG. 3 is a fragmentary view similar to FIG. l illustrating an alternative arrangement of certain parts shown in FIGS. l and 2;

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FIG. 4 is a transverse sectional view taken along lines 4 4 of FIG. 1; v

FIG. 5 is a transverse sectional view taken along lines 5 5 of FIG. l

FIG. 6 is a transverse sectional view taken along lines 6 6 of FIG. 1;

FIG. 7 is a transverse sectional view taken along lines 7 7 of FIG. l;

FIG. 8 is a perspective view of a spacer element shown in FIGS. l, 2 and 3; and

FIG. 9 is a fragmentary longitudinal sectional view taken along lines 9 9 of FIG. 4.

In lthe illustrative embodiment of the invention, the improved stroke-varying meansY is incorporated in an expansible chamber, hammer piston motor, indicated generally byrnumeral 10, comprising a cylinder 12 having a longitudinal bore 14 containing a reciprocating hammer piston 16. The piston has a front striking nose 17 for impacting the shank 18 of a work implement 19. A detachable cylinder head 20 is threadably secured to the rear of the motor cylinder 12 and is provided with a cylindrical recess 22 for housing a fluid distributing valve, indicated generally by numeral 24, comprising a valve, chest 26 and a valve plug 28, the latter providing a rear abutment for the chamber of motor 10. As shown in FIGS. l, 2 and 3, annular spacer elements 30 and 32 are also housed within bore 22 in interchangeable relationship with the distributing valve 24 for a purpose to be hereinafter explained in detail. The cylinder head 20 has a pressure fluid supply chamber 34 to which motive iluid, compressed air for example, is supplied through a passage 36' from any suitable pressure fluid source (not shown). `A suitable manual grip or handle (not shown) t may be formed integrally' with the cylinder head 20; and, such handle may include an operator controlled valve (not shown) for admitting motive iluid to the supply chamber 34.

Formed lin the valve chest 26 is a generally cylindrical valve chamber 38 having reciprocable therein an automatic, pressure iiuid actuated, valve operator 40 of a well knowndiiferential sleeve type. The valve operator 40 has acup-shaped body 41v and an annular flange 42 extending radially outwardly at they forward end of the body 4,1. ,The valve operator'40 is guided on a cy-A lindrical projection 44 extendingjinto the interior of the operator 40 and integrally formedwith the valve plug 28. Surrounding the 'valve chamber 38 at its forward end is an annular recess 46; and, an annular groove 48 opens to valve chamber 38 at a point intermediate the length of the valve chamber 38. Connecting the forward end of the valve chamber 38 to the rear end of the cylinder bore 14 are longitudinal passages 49 which extend through valve plug 28. The annular groove 48 is connected to the forward end of cylinder bore 14 by openings 50 and 51 through valve chest 26 and valve plug 28, respectively, and these openings are alined with a longitudinal passage 52 through the wall of cylinder 12.

. tion between the supply chamber 34 and the supply passage 54. and 59 opening through spacer elements 30 and 32, respectively, communicate between the forward end of opening 51 inthe valve plug 28 andthe rear end of longitu'dinal passage 52 when the spacers are arranged ac-v Similarly, one or both of the passages 58` cording to FIG. 2 or FIG. 3. The cylinder bore 14 is provided intermediate its ends with a piston-controlled free exhaust port 60.

y When the parts are in the position shown in FIG. 1, pressure iluid may flow through passage 36, supply chamber 34, spacer vopenings 56 and 57, supply passage' 54, annular recess 46, through the valve chamber 3S past the forward surface of the valve operator 40 and through passages 49 to the rear end of the cylinder bore 14. The pressure fluid then acts on the rear surface of the piston 16 to drive the latter forwardly to effect its working stroke, i.e. to cause the nose 17 of the piston to impact the extreme rear surface ofthe shank 18, asl shown by broken lines in FIG. 1. After the free exhaust port 60 is overrun by the forward edge of the piston 16, pressure iluid is` trapped in the forward end of the cylinder bore '14 and is compressed and communicated through the longitudinal passage 52, openings 51 and 50, and the annular groove 48 to the upper side of the annular flange 42 to throw the valve operator 40 forwardly from the position shown in FIG. l to the position shown in FIG. 2.

When the valve operator 40 is automatically shifted, as aforedescribed, to the position illustrated in FIG. 2, pressure iluid ows from supply chamber 34, through spacer passage 56 only, the spacer 32 being disposed in an alternate position forwardly of the valve assembly 24, through supply passage 54, past the upper Surface of annular flange 42, around the annular groove 48, through the alined openings 50 and 51 and the longitudinal passage 52 to the forward end of the cylinder bore 12l where the pressure fluidracts on the forward face ofthe piston 16 to drive the latter rearwardly to effect its return stroke. As the hammer Vpiston 16 moves rearwardly from the position shown in broken lines in FIG. 1, the exhaust portj60 will be overrun and continued rearward movement bf the piston will compress the pressure uid trapped in the rear end of the cylinder bore 14. The compressed pressure Vfluid is communicated to the forward end of the valve chamber 38 through passages 49. where it acts upon the lower side of the annular flange 42 throwing the valve operator 40 rearwardly from the position shown in FIG. 2 to the position shown in FIG. l. It will be understood that the aforedescribed shifting action of .the valve operator 40 is repeated in` rapid succession duiring normal operation of the motor 10.

In expansible chamber motors, `such as motor 10, the ir'npulse .delivered to the piston during the power stroke of the motor may be 'altered by varying the period of time during which theY expanding pressure Huid acts upon Y passages therethrough in proper alinement.

wardly from the rear wall of the cylinder head recess 22. From the above description of the operation of motor '10, it will be apparent that, with the spacers arranged according to FIG. l, and assuming a constant supply of pressure fluid, the impulse delivered to piston 16 will be a function of the period of time required for the piston to travel through the bore 14 from its rearmost position to a forward position where the rear pressure face of the piston overruns the free exhaust port 6G. The impulse thereby produced will cause piston 16 to strike the shank 1S with a determinable force. In certain practical applications of percussive tools, it is desirable that the intensity of the hammer blows of motor 10 be increased to meet changed work conditions. In the illustrative tool, this may be simply and quickly accomplished by increasing the hammer pistons stroke and, therefore, the impulse delivered to the hammer piston 16 by rearranging the spacer elements 30 and 32 with respect to the iiuidA distributing valve assembly 24.

As shown in FIGS. 2 and 3, the valve assembly 24 may be axially displaced from the rear end of cylinder 12 by `inserting one or both of the spacers forwardly of the valve assembly. yA's best seen in FIG. 3, the spacer elements 30 and 32 have central bores 62 and 63, respectively, which are coaxially alined with the cylinder bore 14 and are adapted to slidably receive the piston 16. Therefore, when both of the spacers are disposed in the cylinder head recess 22 forwardly of the valve assembly 24, as shown in FIG. 3, the effective length of the cylinder bore 14 and, therefore, the stroke of the hammer piston 16 is increased by an amount corresponding to the combinedA axial dimensions or thicknesses of spacers 30 and 3,2.

When it is desired to vary the percussive action of piston 16 by rearranging the position of spacers 30 and 32 with respect to the uid distributing valve assembly 24 and the cylinder 12, the operator detaches the cylinder head 20 from the rear of the cylinder 12 to expose the spacers and the valve assembly. As seen in FIG. 9 a removable dowel pin 64 penetrates the spacers, the valve chest and the valve plug and is seated in a recess 65 opening from the extreme rear face of the cylinder 12 to maintain these parts and the aforedescribed huid pressure The dowel pin 64 may be removed to permit separation of the spacers 30 and 32 the valve assembly 24 and thecylinder 12 sok that spacers `and the Valve assembly lmay be interthe piston. Such a change in piston impulse may be accomplished by changing the length' of the power stroke of the piston; Accordingly, an important aspect of the present invention is the provision of Van. expansible chamber motor of the above kdescribed type wherein the 1ongitudinal dimension of the motor chamber or cylinder may be altered to vary selectively the operating stroke f the motor piston, thereby to change the intensity of the piston blow delivered to a work element. In the illustrated embodiment of the invention, this may be accomplished by displacing the fluid distributing valve 24, which provides the stationary abutment for the expansible motor chamber, from the rear terminus of cylinder 12 by means of one or more annular spacer elements, such as spacers 3i) and 32, todeline an extension for the expansible chamber and to increase the period during `which expanding motive iluid acts upon piston 16 durchangeably stacked one upon the other in the alternate arrangements, shown in FIGS. `l, 2 and 3, respectively. Thev dowel 64 is then inserted through the spacers and the valve assembly prior to reassembling the cylinder 12 and the cylinder head 20. It will thus be seen that varia-- tionsin the stroke and impact of the hammer piston 16 are very simple and easily accomplished and that it is impossible for an inexperienced or careless operator to incorrectly place the parts.

Referring more particularly to the structure of the; spacer elements 36 and 32, each of these elements comprise annular or tubular bodies having an outside diam-V eter substantially corresponding to the internal diameter of the cylinder head recess 22 and an inside diameter substantially corresponding to the inside diameter of the` cylinder bore 14. As best shown in FIG. 8, which shows. the spacer 30 in perspective, the axial dimension or thick-- ness of the spacer preferably is substantially less than itsl outside diameter. Preferably, the spacers 30 and 32- are of like thickness, whereby the axial dimension of the bore 14 may be extended by an amount equal to the axial dimension of one spacer without regard to which spacer is interposed forwardly of the valve assembly 24.

From the foregoing description it will be apparent thatV the illustrated arrangements of the spacers 30 and 32 and the fluid distributing valve assembly 24 provide the motor 10 with three alternate stroke lengths. varying in like increments. Although two spacer elements have been shown and described, it will also be apparent that the number of spacer elements employed may be more or less than this number, thereby to increase or decrease the number of available variations in the length of the piston stroke. Moreover, the number `of spacers employed in any tool will be determined by the number of increments in tool impacting which are desirable to meet particular work applications. Similarly, the thickness of the spacers will depend upon the iineness or coarseness of control over impacting force which is required in a given application.

While the present blow-varying device has been shown and described as having particular utility when employed with percussive tools having an expansible motor chamber closed by an abutting uid distributing valve, it will be appreciated that the invention broadly contemplates the use of spacer means to vary selectively the axial dimension of the motor chamber by displacing various types of stationary abutments from the motor cylinder and by extending the reciprocative travel of the motor piston into the spacer means. Moreover, it will be understood that the above description and accompanying drawings comprehend only the general and preferred embodiment of the improved blow-varying device vfor a hammer motor and that various changes in the construction, proportion and arrangement of the Various parts may be made without sacriicing any of the enumerated advantages of the invention.

What is claimed is:

1. In a pneumatic percussion tool, in combination: a pressure fluid actuated motor comprising a cylinder, a hammer piston reciprocable in said cylinder and a fiuid distributing valve closing the rear end of said cylinder; a work implement disposed in the front end of said cylinder in blow-receiving relationship with said hammer piston; and spacer means for varying the blow of said hammer piston, said spacer means being insertable between said cylinder and said valve and having a bore therethrough for slidably receiving said hammer piston.

2. 'Ihe invention defined in claim 1, together with a cylinder head detachably secured to the rear of said cylinder and providing a housing for said valve and said spacer means.

3. The combination according to claim 2, wherein said spacer means comprise a plurality of annular spacer elements.

4. The combination according to claim 3, wherein the respective spacer elements and said valve are interchangeably disposed in said cylinder head in stacked relationship to provide selectively a number of different available axial displacements of said valve from the rear oi said cylinder, said number corresponding to the number of spacer elements employed.

5. The combination according to claim 4, wherein respective spacer elements have equal axial dimensions, and said axial displacements of said valve from said rear of cylinder are multiples of the axial dimension of a single spacer element.

6. In a pressure iiuid actuated motor having an expansible chamber defined by a cylinder, a piston slidable in said cylinder and an abutment closing one end of said cylinder, the improvement comprising: piston receiving spacer means insertable between said abutment and said one end of said cylinder to deine an extension for said chamber; said cylinder, said spacer means and said abutment being coaxially arranged in abutting relationship; and said abutment and said spacer means being selectively interchangeable to alter the axial dimension of said eX- tension and the stroke of said piston.

l 7. The invention according to claim 6, wherein said spacer' means comprise at least ,one annular body having a piston receiving bore therethrough, said bore opening to said cylinder and being closed by said abutment.

8. The invention according to claim 7, wherein said spacer means comprise a plurality of like annular elements, and at least one of said elements being arranged on either side of 'said abutment.

9. In a pressure iiuid actuated motor having an expansible chamber defined by a cylinder, a piston slidable in said cylinder and an abutment closing one end of said cylinder, the improvement comprising: piston receiving spacer means insertable between said abutment and said one end of said cylinder to define an extension for said chamber; said abutment and said spacer means being selectively interchangeable to alter the axial dimension of said extension and the stroke of said piston..

References Cited in the tile of this patent UNITED STATES PATENTS 645,582 Watson Mar. 20, 1900 1,083,369 Gendre June 6, 1914 1,219,932 Frost Mar. 20, 1917 1,582,614 Kusunoki et al. Apr. 27, 1926 2,976,844 Goldring Mar. 28, 1961 

